Field of the Invention
This invention relates to apparatus for turning a pair of electrical switches alternately on and off as a function of the pressure of a pressure source, and particularly to apparatus responsive to the input manifold pressure of a motor vehicle engine for controlling the operation of the starter/ignition and the headlight circuits. A pressure responsive piston with a flange connected to the piston shaft actuates a lever which controls the electrical switches.
Description of the Prior Art
Pressure responsive switches in which an electrical switch or contact, or a plurality of switches, are turned on or off in response to a pressure are useful in numerous applications. For example, U.S. Pat. No. 4,616,215 to Maddalena shows a transducer for sensing a vacuum level and producing alarm signals if the pressure is too high or too low. U.S. Pat. No. 4,402,224 to Fukushima shows a device for monitoring vacuum pressure comprising an electric field generator and detector involving a light source and photo detector eventually producing an electrical signal. U.S. Pat. No. 4,008,619 to Alcaide et al measures pressure changes by movement of a diaphragm to change capacitance levels. These approaches to pressure sensing, particularly of vacuum pressures, while useful, are complex and expensive.
Less complex and expensive vacuum pressure sensors which produce switching of electrical circuits are found in U.S. Pat. No. 1,719,049 which shows an ignition switch for automobile engines in which cranking of the engine to start the engine produces a partial vacuum in the manifold which moves a diaphragm to close electrical contacts and complete the ignition circuit. Canadian Pat. No. 210016 measures air pressure from a ventilating system by moving a piston in response to the pressure, and electrical contact pins attached to the piston shaft physically close electrical circuits when the piston is moved to extreme positions to indicate pressures that are too high or too low. IBM Technical Disclosure Bulletin entitled Multiconfiguration Pressure Switch, Volume 8, Number 7, December 1965, shows a pressure switch with a piston movable in response to a pressure, the piston operating a magnet to open or close reed switches positioned adjacent to the path of travel of the magnet, one of the switches being normally open and the other normally closed.